The studies outlined in this proposal are an extension of our original observation that cyanate inhibits the sickling of erythrocytes in vitro. In order to provide a sound basis for long term clinical trials with cyanate, we wish to gain more fundamental knowledge about the mechanism by which carbamylation of hemoglobin S inhibits gel formation and sickling of the erythrocyte upon deoxygenation. The basic question that we will seek to answer is whether the effect of cyanate is due solely to an increase in the oxygen affinity of the cells, or whether there is a direct effect of the solubility of deoxyhemoglobin S after carbamylation. The effect of modification of the NH2-terminal valine residues of hemoglobin S (the site of carbamylation by cyanate) by a variety of other reagents on gelling and on erythrocyte sickling may be instructive. Further studies designed to rule out carbamylation of cysteine-93 of the beta-chain of hemoglobin will be undertaken. The effect of cyanate on carbonic anhydrase will also be studied. The contribution of cyanate to the urea therapy will be approached by a study of the rate of formation of cyanate from urea using simulated clinical conditions. A new sensitive assay for cyanate will be developed. The possible conversion of urea to cyanate in whole blood will be studied in experiments with C14-urea followed by analysis for C14-carbamylated protein.